The present invention relates to a method of checking a test program in a duplex processing apparatus and, more particularly, to a method of checking a test program executed by a standby system simultaneously with execution of a program by an active system.
In a conventional duplex processing apparatus, one of two processors serves as an active processor, and the remaining processor serves as a standby processor. The active processor reads out instructions and data from its main memory to perform on-line operations, while the standby processor executes a test program for checking its normality.
In a conventional duplex processing apparatus, an on-line program runs in the memory for the active processor, and the memories of the active and standby systems are simultaneously updated to duplex the memory contents. A test program for detecting a failure is executed by the standby processor simultaneously with execution of the on-line program by the active processor, thereby preventing the failure of the standby system.
During checking of the conventional duplex processing apparatus, when a failure is detected in the standby system, this is signaled to the active processor. In this apparatus, no problem is posed when the test program normally runs. However, for example, when the standby test program has a failure or overruns due to hardware fault or a software bug, an on-line memory area of the standby processor may be broken. Under this circumstance, since the test program itself overruns, and the standby processor cannot acknowledge the failure to the active processor. As a result, system reliability is adversely degraded.